Bounds on LFV Higgs decays in a vector-like lepton model and searching for doubly charged leptons at the LHC

Abstract

The Higgs-portal lepton flavor violation is studied in a vectorlike lepton model. For evading the constraints from rare $Z\to {\ell }_i^{\pm }{\ell }_j^{\mp }$ decays, we introduce two triplet vectorlike leptons, $(1,3{)}_{-1}$ and $(1,3{)}_0$. The resultant branching ratio for $h\to \mu \tau$ can be up to $10^{-4}$ when the constraints from the invisible $Z$ decays are applied. As a result, the signal strength for $\tau \tau$ channel has a $12\%$ deviation from the standard model prediction, while the muon $g-2$ is two-order of magnitude smaller than the data and $BR(\tau \to \mu \gamma )$ is of order of $10^{-12}$. A predicted doubly charged lepton in $pp$ collisions at $\sqrt{s}=13$ TeV is analyzed and it is found that the interesting production channels are $pp\to ({\Psi }_1^{--}{\Psi }_1^{++},{\Psi }_1^{\pm \pm }{\Psi }_1^{\mp })$. Both single and pair production cross sections of ${\Psi }_1^{++}$ are comparable and can be a few hundred fb. The main decay channels for the doubly charged lepton are ${\Psi }^{\pm \pm }\to {\ell }^{\pm }{W}^{\pm }$ and for the heavy singly charged lepton are ${\Psi }_1^{\pm }\to \nu W^{\pm },{\ell }^{\pm }Z$. The numerical analysis is given at $13$ TeV LHC with $100$ fb${}^{-1}$ luminosity.

Comments: 16 pages, 3 figures, 1 table, version published in EPJC